ABCA1/ABCB1 Ratio Determines Chemo- and Immune-Sensitivity in Human Osteosarcoma

Abstract

The ATP Binding Cassette transporter B1 (ABCB1) induces chemoresistance in osteosarcoma, because it effluxes doxorubicin, reducing the intracellular accumulation, toxicity, and immunogenic cell death induced by the drug. The ATP Binding Cassette transporter A1 (ABCA1) effluxes isopentenyl pyrophosphate (IPP), a strong activator of anti-tumor Vγ9Vδ2 T-cells. Recruiting this population may represent an alternative strategy to rescue doxorubicin efficacy in ABCB1-expressing osteosarcoma. In this work, we analyzed how ABCA1 and ABCB1 are regulated in osteosarcoma, and if increasing the ABCA1-dependent activation of Vγ9Vδ2 T-cells could be an effective strategy against ABCB1-expressing osteosarcoma. We used 2D-cultured doxorubicin-sensitive human U-2OS and Saos-2 cells, their doxorubicin-resistant sublines (U-2OS/DX580 and Saos-2/DX580), and 3D cultures of U-2OS and Saos-2 cells. DX580-sublines and 3D cultures had higher levels of ABCB1 and higher resistance to doxorubicin than parental cells. Surprisingly, they had reduced ABCA1 levels, IPP efflux, and Vγ9Vδ2 T-cell-induced killing. In these chemo-immune-resistant cells, the Ras/Akt/mTOR axis inhibits the ABCA1-transcription induced by Liver X Receptor α (LXRα); Ras/ERK1/2/HIF-1α axis up-regulates ABCB1. Targeting the farnesylation of Ras with self-assembling nanoparticles encapsulating zoledronic acid (NZ) simultaneously inhibited both axes. In humanized mice, NZ reduced the growth of chemo-immune-resistant osteosarcomas, increased intratumor necro-apoptosis, and ABCA1/ABCB1 ratio and Vγ9Vδ2 T-cell infiltration. We suggest that the ABCB1 high ABCA1 low phenotype is indicative of chemo-immune-resistance. We propose aminobisphosphonates as new chemo-immune-sensitizing tools against drug-resistant osteosarcomas.

The Role of Biomimetic Hypoxia on Cancer Cell Behaviour in 3D Models: A Systematic Review

“…3D tumour models are considered to better recapitulate the in vivo tumour microenvironment compared to standard 2D cultures. In this review we have identified a total of 37 publications [ 34 , 50 , 57 , 60 , 62 , 64 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 ] where 3D culture significantly altered cancer cell behaviour towards a more biomimetic response. Eighteen of these studies used 3D scaffold-based cultures and 18 studies used non scaffold-based, cell-generated extra-cellular matrix (ECM) cultures, with a single study using both approaches [ 73 ] ( Figure 3 ).…”

In vitro three-dimensional cell cultures for bone sarcomas

“…3D SaOS2 and U2OS cell spheroids were also generated by using commercial culture plates coated with various matrix: hyaluronic acid, collagen and adhesion proteins (Biomimesys™ matrix, from HCS Pharma, France). By using such an approach, 3D cultures differentially modulated the ATP binding cassette transporter A1 (ABCA1) and B1 (ABCB1, also known as Multidrug resistance protein-1, MDR1) expressions associated with the drug efflux and resistance which has not been observed in 2D environments [70] . 3D culture cells exposed to doxorubicin were characterised by a higher expression of ABCB1 implicated in the intracellular drug efflux, induced by the ERK1/2/HIF-1 pathway.…”

Recent Insights into Therapy Resistance in Osteosarcoma

“…Fanelli et al used a small molecular inhibitor CBT-1 to prevent ABCB1- and ABCC1-mediated efflux, reversing doxorubicin resistance in vitro [ 9 ]. Belsario et al proposed that an increased ratio of ABCB1/ABCA1 indicates higher doxorubicin resistance [ 10 ]. ABCA1 effluxes isopentenyl pyrophosphate, which is known to recruit anti-tumor T-cells, providing a novel immune-stimulatory mechanism to potentially treat osteosarcoma.…”

“…Their study found that tumors high in ABCB1 expression were often low in ABCA1 expression, thus having simultaneous doxorubicin and T-cell resistance. They were able to reverse this phenotype with nanoparticle-encapsulated zoledronic acid, highlighting a potential mechanism to overcome resistance to doxorubicin and immune escape [ 10 ].…”